1. Field of the Invention
The present invention relates to a type of bus, and more particularly to a bus for the High Definition Multimedia Interface (HDMI) that can be manufactured by a simple process, and capable of reducing the distortion caused by the kink effect and the magnetic field interference.
2. Description of Related Art
Traditionally, Cathode Ray Tube (CRT) displays take analogous signals; hence the connectors are designed for transmission of analogous signals, in which a Digital to Analog Converter (DAC) is used to convert digital signals from a display card in a computer into analogous signals, and then the analogous signals are transmitted to a digital display where the analog signals are converted again into digital signals using an Analog to Digital Converter (ADC) circuit. Since signals are first converted from digital to analogous, and then transmitted in analogous form and converted back into digital signals for display, disturbance of signals may occur and cause fidelity losses. If it is possible to directly transfer digital signals to a digital display without any conversions of signals, the problems of signal fidelity losses due to disturbances described above may be effectively prevented. Therefore, digital interface for pure digital signal transmission provides better transmission quality than traditional analogous signal transmission.
To achieve better signal transmission quality, the Digital Visual Interface (DVI) has been developed, which aims principally to connect to computer display cards to provide digital display output functions, for example, displaying RGB signals from computers. Therefore, during the transfer process of the DVI digital interface, the transmission of digital format is entirely unchanged in order to ensure the data integrity along the transmission path from the host computer to the monitor without the disturbance of signals. Thus, better image quality can be displayed on digital displays such as liquid crystal (LCD) projectors, and plasma TV, LCD TV. Product specifications of certain high end products specifically illustrate the features of DVI plug.
Although DVI does provide a better signal transmission quality, it is only used for digital video signal transmission, and is not available for audio portions. For this reason, many manufacturers have redesigned the HDMI bus/port based on the DVI bus/port, wherein such interface encompasses not just video signals but audio parts as well. By loading audio and video signals onto the same cable line, the need for multiple signal line connections is eliminated, enabling safe transmission of uncompressed or compressed high definition video and multi-channel audio signals. Thus, massive high definition and high quality digital contents may be provided to facilitate the reduction of number of connections and usage simplification; therefore, HDMI has become one of the many critical technologies for consumer electronic devices of the new generation. As a result, DVI has become a standard interface for future flat display apparatus.
FIG. 4 illustrates a 3D diagram of a signal transmission line 30 for the HDMI, wherein comprises plural sets of paired conductor lines 311 and 312 bundled in juxtaposition. Conductor lines 311 and 312 respectively comprise copper conductors 311a and 312a which are respectively wrapped with insulation layers 311b and 312b. A layer of aluminum foil 32 is adopted to circumferentially surround the paired conductor lines 311 and 312. A layer of copper braid 33 and a layer of insulation 34 are used to circumferentially surround the layer of aluminum foil 32. In this way, the transmission line 30 is formed and used for signal transmission.
In the transmission line 30, metallic layers such as the aluminum foil layer 32 and the copper braid layer 33 may be used to protect the signal transmission from external disturbance. In addition, paired conductor lines 311 and 312 are twisted together in order to avoid mutual signal interference.
The conventional transmission line 30 is usually in a cylindrical shape with a wider internal diameter. Because the electronic devices, such as LCD projectors, Plasma TV's, LCD TV's or personal computers, are usually installed close to walls, and because the conventional transmission line 30 can not be excessively bent, this makes it impossible to position electronic devices in close proximity of walls and causes inconvenience during installation work.
Meanwhile, when conductor lines are coupled to a connector, each conductor line must be first located to the corresponding position of fixed wire material in the connector in such a way that the transmission lines and the connector can be mutually joined. Thus, assembly operations can be very time-consuming and expensive.
Furthermore, if the coupling direction between the connector at the end of the transmission line 30 and the connector plug on the body of the electronic device mismatch, the transmission line 30 must be turned awry. Due to the significant diameter of the transmission line 30, the interior conductor lines 311 and 312 may be easily broken or damaged, leading to problems of signal transmission failure or bad contact within the transmission line 30.
Because of the significant internal diameter, it might not be easy to bend the transmission line 30 when being plugged into the body of electronic device, and may easily get damaged if excessively bent. Hence, it is important not to overly twist or bend the transmission line 30 with excessive force when connecting to the body of the electronic device.
Since the transmission line 30 is circumferentially wrapped with the layer of aluminum foil 32 and the layer of copper braid 33, the weight of the HDMI transmission line 30 is substantially increased. Thus, the lengthy transmission line 30 must be supported with fixture members in order to avoid possible damage due to the pulling force at the two ends of the transmission line 30.
The structure of the transmission line 30 is much more complicated; in that, the external surface of the conductor lines 311 and 312 are circumferentially wrapped with a layer of aluminum foil 32, a layer of copper braid 33, and an insulation layer 34. Thus, the manufacture of the transmission line 30 requires at least 3 material wrapping processes. Hence, the complexity of manufacturing process would significantly increase the cost.
As mentioned above, the HDMI is one of the major technologies of future multimedia electronic devices, but the structure of the transmission line 30 indeed presents the aforementioned drawbacks. Therefore, resolving the drawbacks described above is an important issue for the manufacturers in the field.